contrMat

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Contrast Matrices

Computes contrast matrices for several multiple comparison procedures.

Keywords
misc, Dunnett, Tukey
Usage
contrMat(n, type = c("Dunnett", "Tukey", "Sequen", "AVE",
"Changepoint", "Williams", "Marcus",
"McDermott", "UmbrellaWilliams", "GrandMean"),
base = 1)
Arguments
n

a (possibly named) vector of sample sizes for each group.

type

type of contrast.

base

an integer specifying which group is considered the baseline group for Dunnett contrasts.

Details

Computes the requested matrix of contrasts for comparisons of mean levels.

Value

The matrix of contrasts with appropriate row names is returned.

References

Frank Bretz, Torsten Hothorn and Peter Westfall (2010), Multiple Comparisons Using R, CRC Press, Boca Raton.

Frank Bretz, Alan Genz and Ludwig A. Hothorn (2001), On the numerical availability of multiple comparison procedures. Biometrical Journal, 43(5), 645--656.

• contrMat
Examples
# NOT RUN {
n <- c(10,20,30,40)
names(n) <- paste("group", 1:4, sep="")
contrMat(n)	# Dunnett is default
contrMat(n, base = 2)	# use second level as baseline
contrMat(n, type = "Tukey")
contrMat(n, type = "Sequen")
contrMat(n, type = "AVE")
contrMat(n, type = "Changepoint")
contrMat(n, type = "Williams")
contrMat(n, type = "Marcus")
contrMat(n, type = "McDermott")
### Umbrella-protected Williams contrasts, i.e. a sequence of
### Williams-type contrasts with groups of higher order
### stepwise omitted
contrMat(n, type = "UmbrellaWilliams")
### comparison of each group with grand mean of all groups
contrMat(n, type = "GrandMean")

# }

Documentation reproduced from package multcomp, version 1.4-10, License: GPL-2

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